Just ran into this today. NXT is listed as a manufacturer; they are English and specialize in planar speakers. The HTIB I had to deal with had this kind of speakers, so maybe it is by them, but there are no codes for NXT! Not in four of the site's Files sections, anyway.
A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw